feat(home): theme CLI tools, add staples, env defaults and mime apps

- Catppuccin Mocha for fzf (colors), bat (catppuccin/bat tmTheme) and
  git delta (syntax-theme + navigate/line-numbers/side-by-side).
- CLI staples on every host: ripgrep, fd, jq, btop, plus gh (SSH) and
  tea (Gitea CLI).
- home.sessionVariables: PAGER, MANPAGER (bat), VISUAL; xdg.enable.
- xdg.mimeApps defaults (web->Firefox, directories->nemo).
- Document the stateVersion pin. README updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

flake.nix

@@ -34,6 +34,18 @@
       url = "github:nix-community/nix-index-database";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+    # treefmt-nix: one multi-language formatter driving `nix fmt` and the
+    # formatting flake check (nixfmt + shfmt + prettier).
+    treefmt-nix = {
+      url = "github:numtide/treefmt-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    # git-hooks.nix: declarative pre-commit hooks (nixfmt/deadnix/statix),
+    # installed into the repo via the devShell.
+    git-hooks = {
+      url = "github:cachix/git-hooks.nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs =
@@ -53,7 +65,7 @@
       let
         # claude-code tracks nixpkgs-unstable regardless of the pinned nixpkgs.
         overlays = [
-          (final: prev: {
+          (_final: prev: {
             claude-code =
               (import nixpkgs-unstable {
                 inherit (prev.stdenv.hostPlatform) system;
@@ -245,7 +257,7 @@
             ];
             homeModules = [
               ./lyrathorpe/home
-              ./system/modules/work/default.nix
+              ./lyrathorpe/home/work.nix
             ];
           };
         };
@@ -268,6 +280,13 @@
         };
       in
       {
+        # flake-parts modules: treefmt-nix wires `nix fmt` + a formatting check;
+        # git-hooks.nix wires the pre-commit check + devShell installation script.
+        imports = [
+          inputs.treefmt-nix.flakeModule
+          inputs.git-hooks.flakeModule
+        ];
+
         systems = [
           "x86_64-linux"
           "aarch64-linux"
@@ -279,26 +298,60 @@
         # nixpkgs instance for that system. Outputs here become per-system
         # attrsets automatically (e.g. devShells.<system>.default).
         perSystem =
-          { pkgs, ... }:
+          { config, pkgs, ... }:
           {
-            # `nix fmt` formatter for the repo.
-            formatter = pkgs.nixfmt;
+            # treefmt drives `nix fmt` and the formatting check below. nixfmt
+            # stays the .nix formatter (the tree is already nixfmt-formatted);
+            # shfmt covers shell and prettier covers markdown/yaml/json.
+            treefmt = {
+              projectRootFile = "flake.nix";
+              programs.nixfmt.enable = true;
+              programs.shfmt.enable = true;
+              programs.prettier.enable = true;
+              # Generated hardware-configuration.nix files are not hand-edited.
+              settings.global.excludes = [ "*/hardware-configuration.nix" ];
+            };
+
+            # Pre-commit hooks: format + lint gate run on commit. The same hooks
+            # are exposed as a flake check (pre-commit.check.enable defaults true).
+            pre-commit.settings.hooks = {
+              nixfmt-rfc-style.enable = true;
+              deadnix = {
+                enable = true;
+                # Unused module args ({config,lib,pkgs,...}) are normal; only flag
+                # genuinely dead bindings.
+                settings.noLambdaPatternNames = true;
+              };
+              statix.enable = true; # reads .statix.toml (repeated_keys/empty_pattern disabled)
+            };
+
+            # treefmt-nix exposes its own `checks.treefmt`; alias it to
+            # `formatting` so the existing CI gate (.#checks.*.formatting) keeps
+            # working without churn.
+            checks.formatting = config.treefmt.build.check inputs.self;
+
+            # deadnix / statix lints as standalone flake checks so `nix flake
+            # check` flags dead code and antipatterns independently of pre-commit.
+            checks.deadnix = pkgs.runCommandLocal "check-deadnix" { nativeBuildInputs = [ pkgs.deadnix ]; } ''
+              deadnix --fail --no-lambda-pattern-names ${./.} && touch $out
+            '';
+            checks.statix = pkgs.runCommandLocal "check-statix" { nativeBuildInputs = [ pkgs.statix ]; } ''
+              statix check ${./.} && touch $out
+            '';
 
             # `nix develop` shell with the tooling needed to hack on this flake.
+            # shellHook installs the git pre-commit hooks into the working tree.
             devShells.default = pkgs.mkShellNoCC {
               packages = with pkgs; [
                 nixfmt
                 nil
                 git
+                deadnix
+                statix
+                treefmt
               ];
+              shellHook = config.pre-commit.installationScript;
             };
-
-            checks.formatting =
-              pkgs.runCommandLocal "check-formatting" { nativeBuildInputs = [ pkgs.nixfmt ]; }
-                ''
-                  # Generated hardware-configuration.nix files are excluded.
-                  nixfmt --check $(find ${./.} -name '*.nix' -not -name 'hardware-configuration.nix') && touch $out
-                '';
           };
 
         # Realise the host tables: each entry becomes a {nixos,darwin}Configuration.